OBJECTIVE: To investigate the effect of a chronic treatment with melatonin on arterial pressure and a possible improvement of the vascular muscarinic and NO synthase (NOS) pathways in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. DESIGN AND METHODS: Mean arterial pressure (MAP), systolic (SBP), diastolic blood pressure (DBP), and heart rate (HR) were evaluated in conscious rats treated with 30 mg/kg per day of melatonin during 4 weeks. Changes in MAP were evaluated following an intravenous injection of the NOS inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME). Relaxant effects of acetylcholine (Ach), sodium nitroprusside (SNP), and the calcium ionophore A23187 were examined on mesenteric beds and aortic rings with or without treatment with melatonin. RESULTS: Melatonin produced a significant reduction of MAP, SBP, DBP and HR in SHR (P < 0.05). L-NAME increased the MAP of melatonin-treated SHR by the same magnitude as that of WKY rats which was significantly higher than that of non-treated SHR (P< 0.05). Melatonin treatment improved the maximal relaxation of mesenteric arteries to A23187 in SHR (P < 0.001) to the WKY level and caused a slight increment in Ach- and A23187-induced vasodilations in aorta from SHR and WKY rats (P < 0.05). CONCLUSION: The present study showed that melatonin exerted a bradycardic and an antihypertensive action in SHR. The enhancement by melatonin of the endothelium-dependent vasodilation (Ach and/or A23187) in mesenteric artery and aorta from SHR and WKY rats and the higher increase in MAP following L-NAME treatment in melatonin-treated SHR suggest the contribution of an improved vascular NOS pathway activity in the hypotensive effect of melatonin.
OBJECTIVE: To investigate the effect of a chronic treatment with melatonin on arterial pressure and a possible improvement of the vascular muscarinic and NO synthase (NOS) pathways in spontaneously hypertensiverats (SHR) and Wistar-Kyoto (WKY) rats. DESIGN AND METHODS: Mean arterial pressure (MAP), systolic (SBP), diastolic blood pressure (DBP), and heart rate (HR) were evaluated in conscious rats treated with 30 mg/kg per day of melatonin during 4 weeks. Changes in MAP were evaluated following an intravenous injection of the NOS inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME). Relaxant effects of acetylcholine (Ach), sodium nitroprusside (SNP), and the calcium ionophore A23187 were examined on mesenteric beds and aortic rings with or without treatment with melatonin. RESULTS:Melatonin produced a significant reduction of MAP, SBP, DBP and HR in SHR (P < 0.05). L-NAME increased the MAP of melatonin-treated SHR by the same magnitude as that of WKY rats which was significantly higher than that of non-treated SHR (P< 0.05). Melatonin treatment improved the maximal relaxation of mesenteric arteries to A23187 in SHR (P < 0.001) to the WKY level and caused a slight increment in Ach- and A23187-induced vasodilations in aorta from SHR and WKY rats (P < 0.05). CONCLUSION: The present study showed that melatonin exerted a bradycardic and an antihypertensive action in SHR. The enhancement by melatonin of the endothelium-dependent vasodilation (Ach and/or A23187) in mesenteric artery and aorta from SHR and WKY rats and the higher increase in MAP following L-NAME treatment in melatonin-treated SHR suggest the contribution of an improved vascular NOS pathway activity in the hypotensive effect of melatonin.
Authors: Luis Girotti; Manuel Lago; Oscar Ianovsky; Marcelo V Elizari; Andrés Dini; Santiago Pérez Lloret; Liliana E Albornoz; Daniel P Cardinali Journal: Endocrine Date: 2003-12 Impact factor: 3.633
Authors: Erika E Nishi; Vitor R Almeida; Fernanda G Amaral; Karin A Simon; Henrique A Futuro-Neto; Roberto B Pontes; Juliana G Cespedes; Ruy R Campos; Cássia T Bergamaschi Journal: Hypertens Res Date: 2019-07-17 Impact factor: 3.872
Authors: Ming Wai Hung; Hang Mee Yeung; Chi Fai Lau; Angela Ming See Poon; George L Tipoe; Man Lung Fung Journal: Int J Mol Sci Date: 2017-05-24 Impact factor: 5.923